#include<bits/stdc++.h>
using namespace std;
int d(int m){
    int r;
    if(m==2||m==1){
        r=1;
    }
    else{
        r=d(m-1)+d(m-2); 
    }
    return r; 
} 
int main()
{
    int s=0,n;
    cin>>n;
    cout<<d(n);
return 0;
 
}
/**************************************************************
	Problem: 1238
	User: wengsihan
	Language: C++
	Result: Accepted
	Time:16 ms
	Memory:2072 kb
****************************************************************/